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SubjectRe: [PATCH 2/3] IRQ: allow check_wakeup_irqs to notice level-triggered interrupts.
On Wed, 25 Apr 2012, NeilBrown wrote:
> On Wed, 25 Apr 2012 10:50:15 +0200 (CEST) Thomas Gleixner
> <tglx@linutronix.de> wrote:
>
> > On Wed, 25 Apr 2012, NeilBrown wrote:
> >
> > > Level triggered interrupts do not cause IRQS_PENDING to be set, so
> > > check_wakeup_irqs ignores them.
> > > They don't need to set IRQS_PENDING as the level stays high which
> > > shows that they must be pending. However if such an interrupt fired
> > > during late suspend, it will have been masked so the fact that it
> > > is still asserted will not cause the suspend to abort.
> > >
> > > So if any wakeup interrupt is masked, unmask it when checking wakeup
> > > irqs. If the interrupt is asserted, suspend will abort.
> > >
> > > Signed-off-by: NeilBrown <neilb@suse.de>
> > > ---
> > >
> > > kernel/irq/pm.c | 6 ++++++
> > > 1 file changed, 6 insertions(+)
> > >
> > > diff --git a/kernel/irq/pm.c b/kernel/irq/pm.c
> > > index 15e53b1..0d26206 100644
> > > --- a/kernel/irq/pm.c
> > > +++ b/kernel/irq/pm.c
> > > @@ -106,6 +106,12 @@ int check_wakeup_irqs(void)
> > > if (irqd_is_wakeup_set(&desc->irq_data)) {
> > > if (desc->istate & IRQS_PENDING)
> > > return -EBUSY;
> > > + if (irqd_irq_masked(&desc->irq_data))
> > > + /* Probably a level interrupt
> > > + * which fired recently and was
> > > + * masked
> > > + */
> > > + unmask_irq(desc);
> >
> > Oh no. We don't unmask unconditionally. What about an interrupt which
> > is disabled, has no handler ..... ? That needs more thought.
>
> If there is no handler, then irqd_is_wakeup_set() should fail should it not?

Well, it does not. The wakeup state is a permanent flag on the irq
line. Though we don't have IRQS_SUSPENDED on that descriptor.

> For disabled: would it be OK to check desc->depth?
> Something like:
> if (desc->depth == 1 && (desc->state & IRQS_SUSPENDED) &&
> irqd_irq_masked(&desc->irq_data))
> unmask_irq(desc);
>

Why not simply managing the pending bit for level irqs ?

Index: tip/kernel/irq/chip.c
===================================================================
--- tip.orig/kernel/irq/chip.c
+++ tip/kernel/irq/chip.c
@@ -379,8 +379,10 @@ handle_level_irq(unsigned int irq, struc
* If its disabled or no action available
* keep it masked and get out of here
*/
- if (unlikely(!desc->action || irqd_irq_disabled(&desc->irq_data)))
+ if (unlikely(!desc->action || irqd_irq_disabled(&desc->irq_data))) {
+ desc->istate |= IRQS_PENDING;
goto out_unlock;
+ }

handle_irq_event(desc);

Index: tip/kernel/irq/resend.c
===================================================================
--- tip.orig/kernel/irq/resend.c
+++ tip/kernel/irq/resend.c
@@ -58,10 +58,13 @@ void check_irq_resend(struct irq_desc *d
/*
* We do not resend level type interrupts. Level type
* interrupts are resent by hardware when they are still
- * active.
+ * active. Clear the pending bit so suspend/resume does not
+ * get confused.
*/
- if (irq_settings_is_level(desc))
+ if (irq_settings_is_level(desc)) {
+ desc->istate &= ~IRQS_PENDING;
return;
+ }
if (desc->istate & IRQS_REPLAY)
return;
if (desc->istate & IRQS_PENDING) {
And to handle interrupts which have been disabled before suspend add:

Index: tip/kernel/irq/pm.c
===================================================================
--- tip.orig/kernel/irq/pm.c
+++ tip/kernel/irq/pm.c
@@ -103,7 +103,8 @@ int check_wakeup_irqs(void)
int irq;

for_each_irq_desc(irq, desc) {
- if (irqd_is_wakeup_set(&desc->irq_data)) {
+ if (desc->depth == 1 &&
+ irqd_is_wakeup_set(&desc->irq_data)) {
if (desc->istate & IRQS_PENDING)
return -EBUSY;
continue;

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